Classifications

• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
  • A23B7/00—Preservation or chemical ripening of fruit or vegetables
  • A23B7/14—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10
  • A23B7/144—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10 in the form of gases, e.g. fumigation; Compositions or apparatus therefor
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
  • A23B7/00—Preservation or chemical ripening of fruit or vegetables
  • A23B7/06—Blanching
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
  • A23B7/00—Preservation or chemical ripening of fruit or vegetables
  • A23B7/10—Preserving with acids; Acid fermentation
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
  • A23B7/00—Preservation or chemical ripening of fruit or vegetables
  • A23B7/14—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10
  • A23B7/144—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10 in the form of gases, e.g. fumigation; Compositions or apparatus therefor
  • A23B7/152—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10 in the form of gases, e.g. fumigation; Compositions or apparatus therefor in a controlled atmosphere comprising other gases in addition to CO2, N2, O2 or H2O ; Elimination of such other gases
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
  • A23B7/00—Preservation or chemical ripening of fruit or vegetables
  • A23B7/14—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10
  • A23B7/153—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10 in the form of liquids or solids
  • A23B7/157—Inorganic compounds
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A40/00—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
  • Y02A40/90—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in food processing or handling, e.g. food conservation

Definitions

• This invention relates to a method of treating vegetable foodstuffs to preserve them, and to hermetically sealed containers of vegetables so treated.
• Raw fresh vegetables are usually preserved by freezing or dehydration, in which case the foodstuff is not sterile, or by canning which involves sterilization by heat and leaves the foodstuff in a more or less cooked state.
• These methods are energy-intensive and freezing or canning may require high initial expenditure on equipment.
• the generally preferred method, freezing not only requires initial expenditure and a great deal of energy for the preliminary treatment, but the frozen products must be transported and stored in a frozen condition. They require a continual input of energy to maintain them fresh, which energy is supplied through expensive installations.
• a method of treating a vegetable foodstuff with sulphur dioxide or a liquid analogue thereof to preserve it characterised in that it comprises the steps of blanching the vegetable foodstuff by treatment in aqueous liquid at a suitably elevated temperature, treating the foodstuff in a solution of pH of 4.8 or less, which solution contains one or more non-toxic or food acids, treating the foodstuff with sulphur dioxide or a liquid analogue thereof either subsequently to or contemporaneously with the acidification and blanching steps, then sealing the treated and cooled foodstuff in a sterile container in the absence of oxygen.
• the foodstuff to be treated may be raw (i.e. uncooked).
• the invention is particularly (but not exclusively) useful with raw vegetables, especially potatoes which are of large bulk in the quantities used, and consequently great in high energy storage costs.
• the pH of the treated foodstuff must generally be no more than about 4.8, and this acidity is provided in accordance with a feature of the invention by one or more food acids or other organoleptically acceptable non-toxic acids.
• the acids which may be used are acetic, malic, fumaric, adipic, ascorbic, succinic, citric and phosphoric acids or, of course, any two or more of any of these acids.
• the foodstuff may be contacted with the acid(s) before the bacteriostasis or sterilisation treatment, or simultaneously therewith if a solution (as opposed to gas) treatment is being effected.
• the acidity is provided essentially by the acids described, although the bacteriostasis or sterilisation treatment may have some small effect on the acidity.
• the treated foodstuff is hermetically sealed in a container.
• a container Whilst any sort of container can be used, we much prefer to use a heat-sealable thermoplastic material container, because these are convenient and very satisfactory.
• the gas and vapour permeabilities of these containers depends on the thermoplastic material(s) used, and the shelf life of the treated foodstuff of the invention will in general be reduced if it is exposed to oxygen permeating into the container.
• low oxygen permeability materials which are resistant to sulphur dioxide and carbon dioxide, such as containers made of laminates of nylon and polyethylene, laminates of polyester and polyethylene and extrusions of ethylene vinyl acetate copolymer with linear low-density polyethylene, for example.
• the bacteriostasis or sterilisation treatment is effected either using sulphur dioxide gas, or a liquid analogue thereof, for example sodium metabisulphite solution.
• sulphur dioxide gas or a liquid analogue thereof, for example sodium metabisulphite solution.
• sterilise but for certain foodstuffs it is sufficient to achieve bacteriostasis, so-that any microorganisms still present will not grow and thus the foodstuff is safe and has a shelf life.
• a ptoferred method comprises the steps of placing the preblanched foodstuff in an open container of heat-sealable thermoplastic material; flushing the foodstuff with carbon dioxide gas; subsequently evacuating the carbon dioxide gas from the foodstuff; flushing the foodstuff with sulphur dioxide gas; evacuating the sulphur dioxide gas from the foodstuff; and heat-sealing the container.
• the initial flushing of the foodstuff with carbon dioxide gas serves to penetrate the plant or animal tissue of the foodstuff and drive out residual air.
• the carbon dioxide also promotes the germination of any bacterial spores within the foodstuff and thus facilitates their subsequent destruction by sulphur dioxide.
• the sulphur dioxide kills yeast, moulds and bacterial cells and spores within ten minutes. It also inactivates enzymes such as polyphenol oxidase.
• the initial flushing with carbon dioxide gas and subsequent flushing with sulphur dioxide gas may advantageously be combined by flushing with a mixture of carbon dioxide and sulphur dioxide gases, for example 5% sulphur dioxide in carbon dioxide.
• the final evacuation must be for a time long enough to ensure that the residual level of sulphur dioxide is lower for each foodstuff than the maximum level permitted for that product by the relevant food regulations (currently in U.K. the Preservation of Food Regulations 1979 - 1982).
• the level should be less than 100 parts per million, at which level the presence of sulphur dioxide can only be detected organoleptically (tasted) in delicately flavoured foods.
• a level of 110 mg per litre has been found by trial to decrease to 50 mg per litre after fourteen days storage; 50 mg per litre is the maximum level currently permitted in potatoes by the U.K. Regulations.
• the energy required in preserving foodstuffs by this method is about half that required for freezing or canning the same amount of food.
• the method can be used to allow produce to be rendered stable for a much lower initial capital cost.
• the foodstuff is pre-prepared before treating, for example peeled and sliced or diced.
• the foodstuff is blanched by heating in an acidic aqueous solution containing permitted acid and optionally also salt.
• permitted acid is meant the food acids etc. listed above. Soaking for a period in the region of ten minutes may be sufficient.
• the pH of the solution should preferably not have risen above 4.0 and the pH of a macerate of the foodstuff particles should preferably not exceed 5.5.
• a solution of 0.02% acetic acid and 1% salt may be used.
• the amount of acid may be adjusted to bring the pH of the prepared solution to 3.7.
• the ratio of foodstuff to solution is preferably in the region of 1:2.
• the containers may be flexible or semi-rigid and can be pouches or trays.
• a preferred method of bacteriostasis or sterilisation according to the invention uses a liquid instead of sulphur dioxide gas.
• the liquids may include solutions of sodium or potassium metabisulphite etc.
• the foodstuff is treated in the solution which may also include the permitted acid and, optionally, also salt.
• the foodstuff may for example be treated for a period in the region of ten minutes or thereabouts.
• the permitted acid is one or more of the food acids etc. described above, preferably malic acid.
• the foodstuff is preferably blanched by treatment with water at a temperature above about 85°C but below about 100°C. This serves to remove oxygen from plant cells, inactivate enzymes such as polyphenol oxidase, and prevent subsequent exudation of plant juices. This latter point is particularly important in the case of potatoes.
• the blanching and acid treatment may be combined, so that the treatment is carried out at blanching temperature for a shorter time, e.g. for about 4 minutes at about 90°C. This simplifies the procedure and improves product quality.
• One example of a preferred treatment solution contains 0.12% - 0.15% sodium metabisulphite and 0.60% - 0.70% malic acid. It may optionally contain salt, for example up to 5%. The balance is water. The pH of such a solution is in the range 1.9 to 2.3 and it contains approximately 400 - 800 mg per litre of total sulphur dioxide.
• the ratio of foodstuff to solution is preferably in the region 1:2.
• a macerate of the product after treatment should have pH less than 4.6 at which spores of major pathogenic bacteria such as Clostridium botulinum will not subsquently germinate.
• thermoplastic material preferably flexible sachets. A high standard of hygiene is maintained during the packing.
• the thermoplastic material should have suitable properties as hereinbefore described.
• the packages are desirably evacuated and flushed with carbon dioxide.
• sachets of foodstuff may be transferred to a vacuum sealer which is evacuated to a vacuum of 850 millibars, and carbon dioxide is then flushed until the vacuum decreases to 250 millibars.
• the package is then heat-sealed.
• a sachet may be sealed by impulse heat-seal, two seals on each sachet being preferred as extra guarantee of integrity.
• potatoes After blanching the potatoes were dried in ambient air until their temperature reduced to a maximum of 40°C. They were filled into pouches made of a laminate of nylon and polyethylene. They were then put into a vacuum sealer and evacuated to 28mm of mercury, carbon dioxide flushed into the packs until the vacuum was reduced to 4mm, and the packs were then sealed by a double impulse sealer.
• sample packs were checked for acidity and S0 2 content.
• the acidity was found to be in the range 4.6 to 4.8 pH and the S0 2 content to be in the range of 100 to 120 mg per litre.
• a further check on 80 2 after 14 days storage showed the level to have reduced to 50 mg/litre. After frying the chips for 4 minutes at 190°C the level was further reduced to 30 mg/litre.
• Potatoes diced to 10mm dice were treated by the process of Example 1, with similar results.
• Potatoes sliced to 4mm thick slices were treated in the same way as in Examples 1 and 2, except that the additions to the initial dip and to the make-up solutions were reduced by 20%. Samples tested after packing were found to have the same levels of S0 2 and acid as in the Examples above. Potatoes chipped to 4mm cross-section, so-called Stringfellow chips, were given the same treatment as sliced potatoes.
• Potatoes chipped to 20 x 10mm cross-section, so-called Steak Chips, were treated by the process of Example 1, except that the additions to the initial dip and to the make-up solutions were increased by 10% from those used in Example 1 above.
• Carrots sliced to 3mm thick slices were treated in the same way except that the additions to the initial dip and the make-up solutions were reduced by 25%.
• Carrots diced to 10mm were treated as whole carrots except that the additions to the initial dip and the make-up solutions were reduced by 15%.
• Parsnips were prepared by the same method as carrots, diced in 10mm dice, blanched for 5 minutes in a similar dip made-up as that used for the diced carrots, air cooled and vacuum packed by the same method as potatoes.
• Swede Turnip was prepared and processed in a similar manner to parsnips.
• Yams were sliced and diced and then prepared and processed in a similar manner to potatoes.
• Small whole beetroot were peeled by carborundum to have a diameter up to 40 mm, and then treated as whole carrots. Beetroot sliced to 3mm thickness were treated in the same manner as sliced carrots.
• Fresh shelled green peas of variety Canners Perfection were packed within one hour of vining. After winnowing to remove extraneous matter and washing, the peas were soaked for 15 minutes in water at a temperature of 25°C and containing:
• peas were then drained and immediately packed in pouches of nylon/polyethylene, which were then evacuated and flushed with C0 2 as has been described in the previous Examples.
• sample peas had pH of 4.84 and contained 100mg/litre S0 2 .
• leguminous vegetables namely broad beans and whole green beans were treated and packed by the same method as peas.
• Blanching temperature was 80°C.
• the florets were than allowed to cool to a temperature of 30°C and then packed in pouches which were processed by the same method as were potatoes.
• Potatoes of the variety Bintje with a dry matter content of 21% and sugar content of 1.5% were peeled and cut into potato chips. The chips were blanched for two minutes in water at 90°C and then rinsed in cold running water.
• the chips were then drained and amounts of 220g each were placed in sachets made of nylon laminated to low-density polyethylene.
• the sachets were put in a vacuum sealer and evacuated, flushed with carbon dioxide, and impulse sealed.
• the packs were tested for residual content of sulphur dioxide after fourteen days and it was found to be 50 mg per litre.
• the packs were stored at a temperature of 21°C for six weeks. After frying the potatoes were found to have organoleptic qualities equivalent to freshly peeled potatoes. The sulphur dioxide content reduced to 25 mg per litre after frying.
• the chips were blanched for four minutes at 90°C in aqueous solution containing sodium metabisulphite (0.148%), malic acid (0.695%) and water (99.157%). This solution had pH 2.3 and contained 400 parts per million of sulphur dioxide.
• the chips were then removed from the solution and air-cooled to a temperature of not more than 30°C. They were then weighed into packs which were evacuated, flushed with carbon dioxide and sealed as previously described.

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Wood Science & Technology (AREA)
• Zoology (AREA)
• Food Science & Technology (AREA)
• Polymers & Plastics (AREA)
• Inorganic Chemistry (AREA)
• Storage Of Fruits Or Vegetables (AREA)
• Preparation Of Fruits And Vegetables (AREA)

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Cited By (7)

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Citations (10)

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• 1986
  • 1986-04-29 DE DE8686303237T patent/DE3664247D1/de not_active Expired
  • 1986-04-29 GB GB8610447A patent/GB2174588B/en not_active Expired
  • 1986-04-29 EP EP86303237A patent/EP0201266B1/de not_active Expired
  • 1986-04-30 AU AU57025/86A patent/AU590272B2/en not_active Ceased
  • 1986-04-30 CA CA000507964A patent/CA1288276C/en not_active Expired - Fee Related

Patent Citations (10)

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